Ignore Tmp Artifacts

Goal

Stop root-level tmp* artifacts from being committed and remove the accidentally committed browser proof PNGs from the current PR branch.

Checklist

• [in_progress] Inspect current ignore rules and tracked tmp artifacts
• [pending] Add ignore rule for root tmp* artifacts
• [pending] Remove tracked tmp PNGs from the branch diff
• [pending] Run the PR gate
• [pending] Commit and push the cleanup

Findings

• .gitignore already ignores /tmp, but not root files like tmp-issue-4900-editor-ai.png.
• The current branch still tracks tmp-issue-4900-editor-ai.png and tmp-pr-4902-editor-ai.png.